The present invention relates to rinsing devices for multi-stage cleaning of containers. In particular, the invention provides a modular rinsing device suitable for removing forming lubrication and gear oil from cans after their manufacture.
The can forming process is a xe2x80x9cwetxe2x80x9d process. The cans are lubricated during the various forming operations and therefore have to be cleaned before they can be coated or filled. Cleaning of the newly manufactured cans is carried out in a number of stages, usually commencing with rinsing the cans in water and/or detergents and finishing with rinsing in de-ionised water. The number of cleaning stages varies, depending upon the material from which the can is made and the finishing processes to be applied to the cans, such as etching, coating etc.
Conventional rinsing devices comprise a plurality of washing and associated drying stages through which the cans are transported on a conveyor belt. The cans are inverted, with their open ends in contact with the belt. The belt is provided by an open-work mat which allows the cleaning solution to be sprayed into and drain from the cans. As the cans pass through the washing stages of the device, high pressure nozzles spray cleaning solution (for example, water) onto the insides and outsides of the cans. After each washing stage, the cans pass into the associated drying stage of the rinsing device where they are dried using air nozzles or air knives directed onto the passing cans. The cleaning fluid drains from the cans through the holes in the conveyor belt.
There are a number of disadvantages with such conventional rinser designs. As the washing and drying stages are generally arranged linearly, along a conveyor belt, and there are usually a number of such washing and drying stages, the rinsing apparatus tends to occupy a large amount of space. Furthermore, as the conveyor belt passes through the washing and drying stages with the cans, the belt has to be washed and dried during each stage of the process, in addition to the cans, to prevent cross contamination in adjacent stages of the rinser. Finally, the spray nozzles and air nozzles are impeded from reaching the insides of the cans by the mat on which the cans are carried. The mat also restricts drainage of the cleaning fluid from the cans.
GB 2041338A describes an apparatus for treating cans, which comprises a number of modules. Each module comprises a pair of drums, which rotate about vertical axes and are used to carry the cans through the various treatment stages. As the cans progress through the device, they are transferred from one drum to the next, thereby minimising cross contamination between stages. Whilst this device is more compact than the conventional rinsing devices described above, it still takes up a significant amount of floor space.
CH 459787 describes a bottle washing device, again comprising a plurality of rotating drums, which transport the bottles through the device. The drums are arranged to rotate about horizontal axes, which lie parallel to one another in the same horizontal plane. By mounting the drums vertically, the floor space occupied by this device is much smaller than that occupied by the horizontally arranged drums described in GB 2041338A. However, a disadvantage of this arrangement is that the liquid used to wash and rinse the bottles remains inside the bottles until they pass through the part of the rotation cycle in which they are in an inverted position.
The aim of the present invention is to provide a modular rinsing device, having a smaller footprint (i.e. area of floor space occupied by the device) than the devices described in the prior art, whilst maintaining adequate drainage of the washing and rinsing fluids from the device. It will be appreciated that to obtain the most compact unit, the transport drums should be mounted vertically (rotating about horizontal axes), but this arrangement does not provide sufficient drainage of cleaning fluid from the containers. For maximum drainage of cleaning fluid, the drums should be mounted horizontally (rotating about vertical axes) with the open end of the containers pointing towards the floor and generally unobstructed. However, this arrangement takes up more floor space.
Accordingly, the present invention provides a rinse module for a rinsing device, comprising at least one circular turret rotatable about a substantially horizontal axis and adapted to transport containers through the rinse module, where they are rinsed with cleaning fluid, characterised in that the or each turret is adapted to support the containers around its periphery with their open ends pointing downwards at all times during the rotation cycle, and the axis of rotation of the or each turret is arranged at an angle to the horizontal sufficient to ensure drainage of the cleaning fluid from the containers by gravity.
The turrets are arranged at a slight angle to the vertical (i.e. with their axis of rotation at an angle to the horizontal). This allows considerable space saving to be achieved, whilst the slight angle ensures adequate drainage of cleaning fluid from the container under the influence of gravity. The containers are mounted around the periphery of the circular turrets, preferably with their longitudinal axes parallel to the axis of rotation of the turret. The containers are supported on the turrets, with as little obstruction of the open end of the container as possible. Mounting the containers in this way, improves access for spray nozzles and air knives, used to wash and dry the containers respectively. The containers are orientated with their open ends pointing downwards to facilitate drainage of the cleaning fluid.
For a straight sided container such as a can, the inventors have determined that mounting the turrets at an angle of 15xc2x0 to the vertical (with their axis of rotation at 15xc2x0 to the horizontal), is sufficient to achieve adequate drainage of the cleaning fluid from the container. Obviously containers having shaped sides or significantly reduced neck diameters may require the turrets to be mounted at a greater angle to the vertical, to ensure adequate drainage.
Preferably, each rinse module comprises a washing stage and a drying stage. The washing stage and drying stage have independent circular turrets to transport the containers through the stage and means to transfer the containers from one turret to the next at the end of each stage. The drying stage minimises the amount of moisture carried by the containers into the next rinse module and therefore reduces cross contamination as the containers pass from one rinse module to the next. Provision of separate circular turrets in the washing and drying stages has the advantage that the drying stage turret remains substantially dry, as only the wet containers are transferred from the washing stage to the drying stage of the rinse module. The drying stage turret is not subjected to the spray of cleaning fluid. Thus, the turret does not have to be dried by the air knives and the containers can be dried more quickly and effectively.
In a preferred embodiment of the invention, the turrets in the washing stage and drying stage are mounted about substantially horizontal axes which are arranged parallel to one another but offset vertically. Thus, the turrets are staggered with respect to one another, with the drying stage turret mounted above the washing stage turret. This arrangement again reduces the footprint of the device and means that the two turrets can drain into the same collection tank.
The containers may be supported around the periphery of each turret between freely rotatable mandrels and a stationary guide rail suitably spaced from, but following the contour of the circumference of turret. In this arrangement, the turret is provided with a number of pockets, defined by adjacent mandrels, with the containers supported in the pockets. The turret is rotated so that the containers are carried past suitably arranged spray nozzles and air knives in the washing and drying stages respectively. Preferably, the guide rails are arranged to apply a slight pressure between the containers and the inner mandrels, so that the containers rotate about their longitudinal axis as they move past the spray nozzles and air knives on the rotating turret. Alternatively, the rotation of the mandrels may be driven, thereby driving rotation of the containers about their longitudinal axis.
Alternatively, the turret may take the form of a xe2x80x9cstar wheelxe2x80x9d with a plurality of pockets located around the periphery of the turret. A stationary guide rail is again used to support the containers, whilst the sides of the pockets drive the containers past the spray nozzles and air nozzles.
Preferably, the contact points on the mandrels, pockets and/or guide rails (where they touch the containers) are made from a low absorbency, non-marking material, such as polyethylene. Contact between the container and the mandrels is minimised by providing rings of material around the circumference of the mandrels, in the form of O rings, for example. Preferably, the material on the contact surface of the guide rails provides sufficient frictional contact with the containers that it xe2x80x9cdrivesxe2x80x9d rotation of containers about their longitudinal axis as they are carried along the guide rail by the rotating turrets.
At the transfer points from one turret to the next, the guide rails are arranged to ensure that the containers are transferred between turrets. As the risk of container jams is highest at these transfer points, the guide rails are preferably adapted to provide access to the turrets in this area, to allow removal of any jam. Access to the pockets at the transfer points may be provided, for example, by a spring loaded portion of the guide rail, which can be opened by an operator to reveal the pockets.
In the washing stages of the rinsing device, cleaning fluid (such as water, de-ionised water or detergents) is sprayed onto the passing containers by spray nozzles mounted along the path of the carrier. Preferably, de-ionised water is used as the cleaning fluid in the last rinse module to ensure that the containers are not smeared or streaky as they leave the rinser. In the preceding rinse modules, water may be used as the cleaning fluid. Preferably, the waste cleaning fluid from each rinse module is collected in an associated reservoir and is used to supply spray nozzles in the preceding rinse module. Thus, the containers are washed using progressively cleaner cleaning fluid as they move through the rinser. This arrangement reduces the water and or detergent consumption of the rinsing device.
The inventors have determined that the volume of cleaning fluid sprayed on to the cans is more important than the pressure at which the sprays operate. Therefore, the nozzles or spray bars in the washing stage of the rinse module are arranged to maximise the flow rate of cleaning fluid passing over the containers. This may be achieved by providing more nozzles or by adapting the design of the nozzles so that they can supply a higher flow rate of cleaning fluid. This allows an effective rinsing device to be provided without using the high pressure pumps, normally associated with conventional rinsing devices.
In a can making line, most of the contaminants on the cans are oil and grease. Where water is used as a cleaning fluid, these contaminants will tend to collect on the surface of the waste water reservoirs and needs to be removed before the water is used in the spray bars of the preceding rinse modules. Floating contaminants may be removed, for example, using a simple weir arrangement. Preferably, the reservoir tanks are of a suitable size to ensure that the water in the reservoirs is held for a sufficient period of time to allow solids to settle onto the base of the tank, before the water is recycled. Larger reservoir tanks also dilute any contaminants draining into the tanks from the rinse modules.
In the drying stages of the rinsing device, air nozzles or air knives are directed onto the passing containers to remove as much moisture as possible before they are transferred into the next rinse module. Preferably, a negative pressure is created inside one or more of the rinse modules, to remove vapour from the containers and keep them as clean as possible. For example, fans may be provided in ducting from the rinse module to extract vapour from that module.
The rinse modules may be provided with the washing stage and drying stage pre-arranged within the module. For example, where the washing and drying stage have separate circular turrets arranged in a staggered formation, the turrets and guide rails may be aligned within the rinse module and fixed in this orientation to ensure smooth transfer of the containers between the turrets. This allows the rinsing device to be set up with any number of rinse modules connected together, using one module as a datum against which the other modules can be aligned. This arrangement also allows simple replacement of a rinse module where necessary.